The present invention relates to a master brake cylinder arrangement for a hydraulic motor vehicle brake system having a housing, in which two adjacent cylinder bores are provided, two piston arrangements, in which a first piston arrangement is received in a first cylinder bore of the cylinder bores such that it is displaceable along a first longitudinal bore axis and in which a second piston arrangement is received in a second cylinder bore of the cylinder bores such that it is displaceable along a second longitudinal bore axis, a force input piston which can be coupled, or is coupled, to a brake pedal and which is displaceably guided along an actuating axis in a cutout of the housing, the first piston arrangement and the second piston arrangement being displaceable according to a movement of the force input piston, in which the first piston arrangement delimits a first pressure chamber with the housing, said pressure chamber being fluidically connected to a hydraulic brake system, and in which the second piston arrangement delimits a second pressure chamber with the housing, said pressure chamber being fluidically connected to the hydraulic brake system.
A master brake cylinder arrangement of this type is known for example from document DE 37 15 209 A1, and corresponding U.S. Pat. No. 4,794,757, both of which are incorporated by reference herein. The construction of this is similar to that of a tandem master brake cylinder arrangement, although it takes up much less space since the two piston arrangements operate in the mutually adjacent cylinder bores which are coupled hydraulically together. Upon braking, a pedal actuating force, by way of which the brake pressure is then generated in the hydraulic brake arrangement, is introduced into the first piston. In other words, in a brake system which is equipped with this master brake cylinder arrangement, the necessary hydraulic brake pressure for acting on the wheel brake of the vehicle is generated solely by the master brake cylinder arrangement.
A directly coupled brake system of this type is disadvantageous in that the driver influences the hydraulic pressure on the wheel brakes in each case by his actuating action on the brake pedal. This is not a problem as long as this is conducive to the braking situation. However, if the driver reacts incorrectly to the actual braking situation, for example by applying too much or too little brake pressure, the braking behaviour, and in particular the braking distance and the path of the vehicle, can become adversely affected, leading in the worst case to an accident.
A further disadvantage of this arrangement is that the two piston arrangements in the corresponding cylinder bores are coupled hydraulically together. The problem with this is that, in the event of a malfunction, particularly a leak in the region of the piston arrangement which is moved directly by actuating the brake pedal, it is no longer possible to reliably control the piston arrangement connected downstream.
The applicant's subsequently published patent application with file reference DE 10 2005 037 792 discloses a master brake cylinder arrangement in which the transmission element is not optimally constructed to absorb eccentrically acting counter forces and resultant tilting moments, which can lead to a malfunction. Eccentrically acting counter forces of this type are caused for example by one of the piston arrangements no longer functioning properly owing to a leak, so that, in the corresponding operating situation, only one of the piston arrangements is still able to act on the transmission element. This means that the transmission element is only in contact with the wall of the housing at certain points, which can lead to a locally delimited high load and a correspondingly high degree of wear.